Fusible plug



1. B. KILKENNY,

FUSIBLE PLUG.

I APPLICATION FILED FEB. 26. 1920. 1,384,471 Patented July 12, 1921.

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BY a m/W A TTORNEYS.

UNITED STATES JOSEPH BERNARD KILKENNY, OF OAKLAND, CALIFORNIA.

FUSIBLE PLUG.

Specification of Letters Patent.

Patented July 12, 1921.

Application filed February 26, 1920. Serial No. 861,525.

To all whom it may concern:

Be it known that l, Josnrn BERNARD KIL- nnNNr, a citizen of the United States, residing at Oakland, in the county of Alameda and State of California, have invented certain new and useful Improvements in Fusible Plugs, of which the following is a speciiication.

This invention relates to a safety appliance primarily designed for instantly relieving the pressure in steam boilers at such time as the water therein becomes low and the rapid evaporating of the water by the intense heat of the fire in the fire-box endangers the exposing of the boiler-crown sheet subjecting the boiler to undue strains and in fact, in jury.

The principal object of the invention is to provide a safety applianceof what is commonly termed the fusible type, and which when operated will permit the steam to escape from the boiler into the firebox through a plurality of vent openings or ports, whereby the steam will be distributed over the fire-box area, thus instantly reducing the fire and at the same time serving as an alarm to the boiler attendant that the water in the boiler is at such a low point as to endanger the same. To provide a con struction of the fusible type wherein the fusible element is capable of beino' readily replaced from a point within the firebox, and also enabling the fusible element sup porting shell to be inserted preferably in the crown-sheet from a point within the firebox, and to further provide a construction whereby the ports of the fusible element shell for directing the steam flow into the fire-box may be utilized in positioning or removing the shell from the crown-sheet.

In the drawings, Figure 1 is a vertical sec tional view, illustrating the preferred embodiment of my invention in position in an opening in a boiler crown sheet.

Fig. 2 is a transverse sectional view taken on the line 22 of Fig. 1, viewed in the direction of the arrow.

In the drawings 1 indicates a boiler crown plate or sheet of any well-known construc tion and through a threaded opening 1 thereof, is received the tubular shell 2 of suitable metal, the upper end of which projects a short distance beyond the inner surface of the plate or sheet 1, and under normal conditions, namely, when the boiler contains water to the level above the sheet or plate 1, said shell extends thereinto and is maintained cooled thereby.

A chamber 3 is formed interiorly of the shell 2, the same terminating at the upper end of the shell in a passage a and at the lower end of said shell in a threaded bore 5, both said passage 4 and bore 5 preferably of a diameter less than that of the interior of said chamber 3, providing an annular flange 6 at the base of said chamber and a corresponding flange 7 at the upper end of said chamber. A shoulder 8 is also formed upon the interior of the. chamber immediately below the flange 7.

The flange 6 at the base of the shell 2 is provided with the spaced vent channels 9 connecting the base of the chamber 3 with the interior of the boiler lire-box, said channels being inclined toward the outer edge of the shell 2 and providing a means for the reception of a tool for facilitating the positioning of the shell within or the removal of the same from the boiler crown lathe or sheet. The channels 9 further provide a means for directing the steam released from the boiler in a manner hereinafter described over a Wide area of the fire, to reduce the heat thereof and also to warn the boiler attendant of the operation of the device due to the water in the boiler running low.

Removably positioned within the chamber 3 of the shell 2 is a suitable plug 10 adapted when the shell is in position as in the drawing to be inserted thereinto from a point within the fire-box through the opening 5. A portion of the plug extending into the chamber 3 is of a diameter approximately equal to that of the opening 5 insuring a space around that portion of the plug within the channel 3, said space being insured by extending the plug centrally through the chamber and forming the chamber of a diameter larger than that of the opening 5. To facilitate the positioning and removal of the plug relatively to the shell 2 said plug is preferably formed on its lower end with a wrench receiving portion 11 which falls short of overlying the lower discharge ends of the channels 9. The plug is formed longitudinally of its center with a fusible element receiving bore 12 opening at the opposite ends of the plug and from said bore, approximately midway in its length extend the laterals 13, the outer ends of which are disposed to lie slightly above the. upper surface of the flange 6 when the parts are assembled as in the drawing.

At a point immediately below the connection of the laterals 13 with the bore 12, said bore is restricted by an annular shoulder- 14 and from said shoulder the upper end of said here is preferably outwardly flared as at 15, and below said shoulder the walls of said bore are preferably parallel as illustrated.

The bore 12 and lat rule 13 are filled with a suitable fusible element 16, preferably poured thereinto when the plug is removed from the shell 2. The upper end of said element projects above the upper end of the plug 10 as at 17, the projecting portion being of a diameter corresponding to that of the passage 1- and preferably of a length to lie flush with the upper surface of the shell when the plug is positioned therein, as in the drawings, T he plug 10 at its upper end is of a diameter to snugly fit within the confines of the shoulder 8 and to contact with the under surface of the flange 7, said contacting portion of the plug and shell together with the snug fit of the portion 17 of the ele ment 16 with the wall of the opening 4 pre vents the escape of steam or water from the boiler into the chamber 3 until such time as the element 16' is melted, as hereinafter described. 7

The device when assembled as illustrated in the drawing operates in the following manner 0n the lowering of'the water level in the boiler to a point to expose the upper portion of the shell 2 the fire box heat passing through the vent ports 9 materially raises the temperature of the plug 10, over that when the shell surround d by water, consequently this increased temperature permits the rapid fusing of the element 16, at which time the boiler steam pressure displaces the same from the bore 12 and laterals 13 perinitting'the released steam pressure in the boiler to escape therefrom through said bore 12 and laterals 13. The tapering of the bore 12 as in the drawing and the providing of thefiange or shoulder 14: which restricts the lower end of said bore causes the steam admitted through the upper end of the bore to be forced laterally under pressure through said laterals 18 into the chamber 3 from whichit escapes in theform of jets through the relief channels 9, which direct the released steam over a wide area ofthe fire enabling the fire to be reduced by this steam volume at the time when the boiler water is low and also relieving the boiler pressure. After the device is operated and it is desired to insert a new one prior to refitting the boiler, it is only necessary that the old plug be removed and a new one inserted in its place. By constructing the casing or shell side walls as in thedrawing, it is possible to insert or remove the shell from the crown sheet opening from a point interiorly of the said plug provided with lateral channels communicating with the enlarged chamber whereby the fusing of said element provides a connection between the boiler water space and the firebox through said enlarged chamber.

2. A safety appliance for steam boilers comprising atubular shell exposed at one end to the interior of the boiler waterspace and at its opposite end to the boiler fire-box, said shell provided on its interior with an enlarged chamber and at one end with relief conduits connecting said chamber with the interior of the boiler fire-box, a tubular plug rcmovably positioned within said shell for closing one end of the tubular portion'thereof, the tubular portion of said plug being restricted adjacent one end and having late a l channels extended therefrom to provide communication with the shell chamber, and a fusible element positioned within said plug for closing the channel therein and the lat erals thereof, the opposite'ends'of said fusible element being exposed one to the boiler water chamber and the other to the boiler fire-box.

' In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses. V v

JOSEPH BERNARD KILKENNY. Witnesses: V

HARRY A. ToTrnN, D. B. RICHARDS. 

